788 



MACROSCOPIC AND MICROSCOPIC CHARACTERS OF PLANTS. 



The cork cells, the cambial cells, and the thin-walled, 

 rectangular cortex cells are larger in the hybrid than in 

 either parent. (Table J 4.) 



Table J 4. — Size of cork cells, cork cambial cells, and cortex cells. 



There may be present in a section of the cortex in 

 I. coccinea 3 to 4 sclerenchymatous patches. Such 

 patches are not seen in 7. quamoclit, but there may be 1, 

 never more, in the hybrid. 



No definite dividing line exists between the cortex 

 and the vascular cylinder. 



Pitted vessels in the wood are often grouped together 

 in twos, threes, and fives in I. coccinea; sometimes in 

 twos in I. quamoclit; and often in twos and threes in the 

 hybrid, but not so much grouping as in I. coccinea, yet 

 more than in I. quamoclit. 



The largest vasa in I. coccinea are in a zone a short 

 distance interior to the outer layer of wood ; in I. quamo- 

 clit at the exterior of the wood ; and in the hybrid in a 

 zone that is nearer the exterior than in I. coccinea, but 

 nearer the interior than in 7. quamoclit, that is, in a 

 mid-intermediate position. 



The diameters of the pitted vessels are: 7. coccinea 

 104.5/*, 7. quamoclit 75.5/*, 7. sloteri 97/*. The diameters 

 of largest pitted vessels are: 7. coccinea 169/*, 7. quamo- 

 clit 126/*, 7. sloteri 169/*. 



The cylinder is broken up by 4 rather wide medullary 

 rays into 4 wedges in 7. coccinea; the 4 rays are nar- 

 rower and less distinct in 7. quamoclit; and they are not 

 quite so distinct in the hybrid as in 7. coccinea, yet more 

 distinct than in 7. quamoclit. The width in the hybrid 

 is intermediate. 



No pith is present, a tetrarch protoxylem takes up 

 the center of the cylinder. 



Stem. 



Transverse sections of the stems of I. coccinea, I. 

 quamoclit, and 7. sloteri were taken just below the first 

 branch. 



The epidermis is, in all 3, a layer of cells of the same 

 depth, but in the hybrid the cells are of a greater width 

 than in either parent. 



The widths of the cells of the epidermis are : 7. coc- 

 cinea 29/i, 7. quamoclit 22/*, 7. sloteri 43/*. 



Cuticle is developed on the outer walls. In the 

 hybrid the epidermis appears rather indistinct and in 

 places it has fallen off, due probably to the greater 

 development of cork in the hybrid, there being 2 layers 

 in it, and but 1 in each parent. The cork cambial cells 

 of the hybrid are larger than in either parent. 



The sizes of the cork cambial cells are: I. coccinea 

 36 by 7.2/*, 7. quamoclit 18 by 7.2/t, 7. sloteri 40 by 15/*. 



The cortex consists of a cylinder of rounded cells, 

 the smaller cells toward the exterior. A complete corti- 

 cal cylinder of 2 to 3 layers, this number being increased 

 to 6 in the region of least development of wood, is found 

 in 7. coccinea; there being 2 to 3 cortical layers in 

 7. quamoclit and 5 layers in the hybrid. 



The endodermis is very distinct and well defined in 

 I. coccinea, but not so well defined in 7. quamoclit and 

 the hybrid. In the hybrid, however, the cells are much 

 larger in both dimensions than in either parent. 



The sizes of the endodermal cells are: 7. coccinea 

 54 by 22/*, 7. quamoclit 50 by 11/*, 7. sloteri 90 by 36/*. 



The outermost layer of phloem has some of its cells 

 sclerosed. At the junction of each 2 endodermal cells 

 there is at least 1 sclerosed cell. In 7. coccinea, in a few 

 places, there may be 2, 3, or up to 7, of these cells joined 

 together. In 7. quamoclit there is almost a continuous 

 ring of such cells inside of the epidermis — one reason 

 for which arrangement is that the endodermal cells are 

 shorter than those in 7. coccinea, thus bringing the 

 sclerosed cells at the junctions nearer to each other; 

 another reason is that some cells between those at the 

 junctions have also become sclerosed. In the hybrid 

 there are either 1 or 2 sclerosed cells at each junction of 

 2 endodermal cells, but they appear much farther apart 

 and much less numerous than in either parent on account 

 of the much greater length of the endodermal cells. The 

 sclerosed cells in the hybrid are intermediate in size 

 between those of the two parents, but slightly nearer 

 those of 7. coccinea. 



The diameters of the sclerosed cells are : 7. coccinea 

 29/*, 7. quamoclit 18/*, 7. sloteri 25/*. 



The phloem, which is composed of sieve tubes, phloem 

 cells, secretory cells, and chambered crystal cells, is in 

 both parents less developed on the two sides where there 

 is also less development of the wood, but in the hybrid 

 is evenly developed on all sides. The secretory cells in 

 7. quamoclit are the most numerous, there being on the 

 average of 2 to each microscopic field, while in 7. cocci- 

 nea and the hybrid there is an average of 1. The phloem 

 of the hybrid contains more chambered crystal cells 

 than in either parent. 



The numbers of chambered crystal cells are : 7. cocci- 

 nea 14, 7. quamoclit 1 in 2 fields, 7. sloteri 16. 



The ivood cylinder in the stems of all three plants 

 consists of an innermost circle of primary bundles, and 

 an outer continuous zone of wood cells and fibers. There 

 is an irregular development of wood due to the flattening 

 of the stem. In 7. quamoclit, on the 2 narrow sides, there 

 is no secondary wood, while in 7. coccinea and the hybrid 

 there is, but the cell walls have not become thickened. 

 The other two sides have a much greater development of 

 secondary wood with thickened cell walls. The develop- 

 ment of wood in the hybrid is much greater than in 

 either parent. 



In the hybrid, just outside the phloem, between it 

 and the endodermis, are extra bundles with xylem in the 

 center surrounded by a zone of phloem. Transverse sec- 

 tions of the stem taken below the first and second 

 branches have these bundles present, but sections below 

 the third branch do not. 



The largest vasa in the stem are larger in the hybrid 

 than in either parent — in 7. coccinea 180/* in diameter, in 

 7. quamoclit 144/*, in 7. sloteri 216/*. 



There are 9 protoxylem patches in 7. coccinea, each 

 having on its inner side a small patch of intraxylary 

 phloem which contains a very few crystal cells. There 

 are many protoxylem patches and intraxylary phloem 

 patches with many crystal cells in 7. quamoclit, form- 

 ing an almost complete zone. There are only 4 distinct 



